DE 1515023 discloses a conventional heating system. A piece of suitable wire is wound up as to form a coil around heat stable core material. The unit is sandwiched between further heat resistive layers.
The respective unit is then normally placed into a heat transfer block, for example an aluminium block. In the case of an iron the block can provide the sole of the iron. Pressure is normally applied as to make sure that a good thermal contact between the internal resistive heating element and the surrounding aluminium block is made. A conventional temperature sensor, in the form of a NTC-unit, is often arranged next to or inside the heat transfer block and held in position using a heat resistive foil.
WO 2007/131271 A1 discloses an improved temperature sensor for an electric heating vessel. The temperature sensor can be an electronic heating sensor being thermally insulated from the heat distribution plate, but in thermal communication with the contact plate.
EP 1 370 497 B1 discloses a sol-gel derived resistive and conductive coating. Disclosed is in particular a composition for application to a substrate to form a coating thereon, the composition comprising a sol-gel solution in which up to about 90% of said solution is a conductive powder.
In view of the prior art the present invention aims at providing an optimized heating element, which comprises a heating unit, a heat transfer unit, and a temperature sensor. It is desired that the unit can be manufactured efficiently in a low-cost mass production process and that the temperature sensor is provided in a form optimized for such process and at the same time efficient for accurate and reliable temperature measurement.